Caisson.



Paemad Mug. im, wim.

M Shams-Sheet W. H. MCFAEN.

(No Model.)

.imi

Patented. Aug. 28, |900.

W. H. MCFADDEN.

C A I S S 0 N (Application lcd June 27, 1900.1

I4 Shees-Sheei 2.

(No Model.)

-NMI

w.. '.ufaiag.. b1 Awyf Panamal Aug. 2s, |900.

W. H. MCFADDEN.

CAISSON.

(Application led June 27, 1900.)

I4 Sheets-Sheet 3.

(No Model.)

WITNESSESI fm. L

1m: Nonms 'PETERS co.. PHOTO-uma., WASHINGTON, D. c.

Patented Aug. 287 |900.

W. H. MCFADDEN.

CAISSON.

(Application filed June 27, 1900.)

I4 Shasta-Sheet 4.

(Nu Modal.)y

INVENTOR ma Nonms PETzns ca. Priore-uma.. wAsmNGmN. u c.

Patentn Aug. 20, |900.

lw. H. McrAnnEN.

CAISSON.

(Appicntion filed J'une 27, 1900.!

I4 Sheets-Sheet 5,.

(N0 Model.)

Atty.

WITNESSES: fh,

Tm: mams Psrsns co.. morumo.. WASHINGTON, u. c.

Patented Aug. 28, |900.

W. H. MGFADDEN.

CA I S S 0 N (Applicatomled' Juna 27, 1900.)

I4 Sheets-Sheet 6.

(No Modeh) 1H: Noam: Perma co vnoroumm WASHINGTON, D. c,

Patented Aug. 28, 1900.4

Att'y.

C A l S S 0 N (Application led June 27,' 1900.)

w. H. mFA'nmsm.

(No Model.)

IIIW//IIII/III//IIIIIIII/II/ 1H: Noms Pfrzns co.. Pnmouwo.. WASHINGTON, o c

WIT ESSES Patented Aug. 28, 19001.

CAISSON.

(Application filed June 27, 1900.)

w. H. McFAnnEN.

I4 Sheets- Sheet 8.

(No Model.)

FIEJZ- INVENTOR ma News Pneus ca. Puo-muws.. WASHINGTON. D c.

Patented Aug. 28, |900 C A l S S 0 N (Application led June 27, 1900.)

I4 Shees-Sheet 9.

(No Model.)

me scams Ferias co.. nom-mmc.. wAsmNnToN. D. c.

No. 656,350. Patented Aug. 28, i900. w. H. MCFADDEN.

CAISSON.

(Application filed June 27, 1900.) (No Model.) I4 Sheets-Sheet la).

wn' EssEs: INVENTo 7%. Het, :5I

l, i u) i Aft'y.

Tn: Noms Patins co. Pno'ruumo.. wAsHlNcToN. n. c.

(No Model.)

FIG/7.

WIT

ESSES:

(Application filed. June 27, 1900.)

I4 Sheets-Sheet Il.

mvlsnrroR` wdhmlilwlwldw Tu: Nowms PETERS co., Pno'ruuwo.. wAsHmaroN, D. c.

N0. 656,850. Patented Aug. 28, |909.

W. H. MGFADDEN.

CAISSON.

(Application led June 27, 1900.) (N o M o d el I4 Sheets-Sheet l2.

W TNESSES:

C.. ...W Mw Atty. m

YH: mams PETERS am. Puo'l'dtlfual. wAsHmcToN. n: c.l

Patented Aug. 28, |5100.

W. H. MGFADDEN.

CAISSON.

(Application filed June 27, 1900.)

i4 Sheets-Sheet I3.

(No Model.)

F/E. m.

ITNESSES: f2

I4 Sheets-Sham I4.

Patented Aug. 2S, |900.

W. H. MCFADDEN.

CAISSON.

(Application fxled June 27, 1900.)

(No Model.)

INVENTOE.

Atty.

me Nonms Pernis co. Pnomumo., wAsNmTuN. o. c.

calsson.

STATES f PATENT OFFICE.

srEcIEIcATIoN forming part of Letters Patent No. 656,850, aerea Augustae, 190e. Applicationled .Tune 27, 1900. Serial No. 21,748. (No model.)

Y To all whom, it muy concern:

Beit known that I, WILLIAM H. MCFADDEN, a citizen of the United States, residing at Pittsburg, in the county of Allegheny and State of Pennsylvania, 'have invented or dis-v covered certain n ew and useful Improvements in Caissons, of which improvements the following is a specification.

The invention described hereinrelates to certain improvements in apparatus for dredging and removing earth, stones, dac., from the bottoms of rivers, lakes, &c., and also for the leveling up of the bottoms of such bodies of water or for clearing or cleaning the same, as desired.

Among other things the invention has for one object a construction of caisson and hoisting mechanism connected therewith whereby the continuous removal of material from the caisson may be effected without in any way interrupting or disturbing the fluid seal, whereby a certain predetermined pressure can be maintained in the caisson to prevent the ingress of water.

It isV a further object of the invention to provide for an extension of the caisson, so as to render it available at different depths.

The invention is hereinafter more fully described and claimed.

In the accompanying drawings, forming a part of this specilication, Figure l shows a iioat having my improved caisson connected to one end thereof and also provided with suitable mechanism-such as dippers, buckets, and clamshells-'for the removal of dirt, tbc., from thebottom of the river, dre., and mechanism for operating such devices. Fig. 2 is atop plan View of the same. Fig. 3 is aview in side elevation, showing the caisson separated a short distance from the float or scow, but having suitable connections by pipes to pumps and air-compressors located on the float. Fig. a is a view in elevation, showing the caisson entirely detached from the scow or VIloat and having the pumps and compressors mounted thereon. Fig. 5 is a view in elevation ofthe upper portion of the caisson, showing the air-chamber and a portion of the superincumbent tank, whereby weight may be imposed on the caisson for forcing the latter down, as hereinafter described. Fig. 6 is a sectional elevation of the upper portion of the caisson, the plane of section being indi cated by the line VI VI, Fig. 7. Fig. 7 is a sectional plan view, the plane of section be- ,ingindicated by the line VII VII, Fig. 6. Fig.

S is a sectional detail view illustrating the brake mechanism for the bucket-hoist. Fig. 9 is a sectional detail view on'V a plane indicated by the line IX IX, Figs. 6 and 7. Fig. 10 is a sectional elevation through the airchamber, locks, and motor-chambers on a plane indicated by the line X-X, Figs. 6 and 7. Fig. ll is a view, partly in section and partly in elevation, of the discharge-conduit on a plane indicated by thewlinel XI XI, Fig. 7. Figs. 12 and 13 are detail views of the discharge-conduit. Fig. lflis a'seotiolnal plan on a plane indicated by line-XIV XIV, Fig. l2.Y Figs. 15 and 1G are sectional elevations of the lower portion of the caisson, the planes of section being indicated, respectively, by the lines XV and XVI, Fig. 17. Fig. 17 is a `section al plan view on planes indicated by the lines XVII XVII, Fig. l5. Figs. 18, 19, and 20 are views in elevation showing the manner of guiding and supporting the upper part of the caisson as against lateral movement and also supporting the airchamber and submerging-tank while adding orremoving sectionsof the lower portion of the caisson.

In the practice of my invention the float or scow l is provided at one end with a recess in which is located the caisson to be hereinafter described. On the float and around the edges of the recess are secured posts and uprights 2, which serve as lateral supports and guides for the caisson in its vertical move-l ments. When the caisson is resting upon the bottom, the surface movement of the water will impart an oscillation to the float or scow, which would tend if the posts or uprights bore directly on the sides of the caisson to sway the latter back and forth. In order to permit acertain amount ot movement of the scow independent of the caisson, bearingboards 8 are movably mounted on the frame, of whichthe posts 2 form a part, their lower ends resting upon cross-timbers 4, as clearly shown in Figs. 18, 19, and20. These Abeards are pressed against the sides of the caisson by means of springs 5, having one end secured to the frame, while their opposite ends bear against the rear sides of the boards.

IOO

These boards are held with the freedom of inand-out movement by means of bolts (V5, passing loosely through the boards and secured to the frame. It will be readily understood that by this construction a certain amount of oscillation of the scow is permitted without materially disturbing the vertical position of the caisson. For the purpose of supporting the air-chamber and submerging-tank when it is desired to shift the float and caisson or to insert or remove sections thereof supporting-arms 7 are pivotally mounted upon the scow in such relation to the normal position of the-caisson that the arms can be swung in under lugs 8, formed at the lower end of the air-chamber.

The caisson consists, essentially, of an airchamber, a submerging-tank E, arranged above the air-chamber B, a working chamber C at the lower end of the caisson, a tubular shaft or tunnel connecting the air-chamber and Working chamber, and a discharge-conduit, as will be hereinafter described.

As shown in Figs. 5 to 8, the air-chamber consists, substantially, of a metal shell having on opposite sides double Walls 9 and 10, each provided with doors 11 for the ingress and egress of the workmen. These doors are constructed in the usual or any suitable manner and provided with suitable locks, whereby they may be firmly secured in a closed position and when so secured hermetically seal the spaces or chambers A between the double Walls. Within chambers D, formed above the air-locks and providedvwith doors 11a, are placed electric motors 12 and 13. The motor 12 is employed for operating through suitable gearing and counter-shaft 12W, the vertical shaft 14 extending down to or toward the lower end of the caisson and employed for shifting the digging-bucket, as will be hereinafter described. The motor 13 is connected by suitable gearing to the shaft 15 within the main chamberB, and on said shaft is secured a drum 16 for hoisting a bucket 17. This bucket can be used with the conveyer or digging buckets, hereinafter described, for the removal of dirt, &c., from the bottom of the caisson, but is generally employed for the removal of large stones or other substances which would not pass readily through the discharge-conduit. The rope 18, by which the bucket is raised, passesaround a guide-pulley 19, secured to the top of the air-chamber B, and around a pulley 20, mounted on an arm 21, attached to the vlid or cover 22 of the discharge-box 23. This discharge-box extends through the bottom of the air-chamber into a receiving-chamber 24, secured to the under side of the airchamber. The lid 22 when in normal or closed position forms a tight joint with the edges ofthe box, so as to prevent any material loss of air. yAs the bucket is raised the bail thereof will strike against the arm 2l, so as to lift the lid 22 on the continued upward movement of the bucket, which as soon as it reaches discharge position, as shown by dotted lines in Fig. 7, will tip, its holdinglock being released, and discharge its contents int-o the box 23. On the shaft 15 is secured a disk 25, having a strap 26 arranged around it, one end of said strap being connected to a suitable stationary support, while the opposite end is connected to one arm of a bell-crank lever 27. The opposite end of this bell-crank lever is connected to a suitable As soon as the contents of the bucket have been discharged into the box the controller of the motor 13 and solenoid 28 is reversed, so as to break the circuit of the solenoid, allowing the bucket to drop, and thereby permit the closing of the lid 22.

In order to remove dirt, stones, dac., from the receiving-chamber 24 and also to prevent the loss of air when the lid 22 is opened, as before stated, the box 24forms a part or enlargement of a pipe 30, through which water is caused to liow in a sufficient volume to entirely fill the pipe and with a pressure or head equal to and preferably a little above the pressure of the air within the air-chamber B. This pressure or head Within the pipe 30 is produced and maintained by reducing the discharge-orifice beyond the carrying capacity of the pipe and forcing in a supply of water in excess of the delivery capacity of such orifice. This stream of water not only serves to remove dirt, dre., from the box 24, but also as a seal to prevent the escape of air from the air-chamber when the lid 22 is opened. In case the rocks, dac., discharged into the chamber 24 cannot be removed through the pipe 30 the box is provided with a removable bottom 31, hinged to one side of the box and held in position by any suitable form of lock 32. After the lid 22 has been closed the bottom 31 can be opened and the rocks or other substancesremoved without any loss of air, except such small volu me as may be contained within the boxes 23 and 24. The discharge-pipe 30 is also provided with a removable section 30a for the removal ofV any substance which cannot be removed by the water.

The tunnel or tubular shaft connecting the air-chamber with the working chamber at the lower end of the caisson is formed of a series of sections 33, provided at their ends with inwardly-projecting flanges 34, whereby they may be bolted together and to the under side of the air-chamber and the top of the working chamber C. Each of these sections is provided with brackets 35, having their outer IIO . essere s ends suitably shaped to .form bearings furthe duced into the tubular shaft or tunnel, the

driving-shaft sections '14 are connected to i gether` by couplings 37, thereby forming a continuons drivin g-shaft for the entire length of the caisson.

YAs shown in Figs. l5, 16, and 17, the working chamber C consists of a cylindrical metal shell open at its lower end-and provided at its upper end with iianges 3S, 'whereby it mayv be bolted to the lower sectionv 33 of the con- :looting-tunnel. Vlithin thisworking chamber is arranged the lower end of the dischargeconduit 39, which enters through a stungbox 4:0 in the upper end of the Working chamber at one side of the tubular shaft or tunnel 33 and is capable of movement up and down in said chamber, as will be hereinafter described. The conduit is held in position in theworlring chamber by vertical guides 4l, to which the conduit is attached by means of bolts 42, as shown in Fig. 17. The lower end of the conduit is closed, but is provided with an' upwardly-projecting branch 43, into which the dirt to be removed is discharged by buck- Iets la on an endless belt passing around a driving-pulley and a guide-pulley d6. The pulley l5 is mounted on a shaft which has bearings 'in the sides of the turning-head 4.8.l

The bearings for the shaft of the guide-pulley 4G are made movable on the side plates t7, so that by the turning of the adjustingscrows or nut 4:9 the tension of the belt carrying the buckets can be regulated as desired. I lhe turning-head is p.: ovided at its upper end with a stem 50, extending through a bearing 5l, formed at the end of a bracket secured to the wall of the working chamber. At its lower end the turningdiead is provided with a tuu bnlar stem 52, fitting loosely into the upper end of the branch pipe 43, as shown 'in hig. l5. .es the parts are' so proportioned that the upper endbf the branch 43 is nearly in the center of the working chamber, the frame carrying the buckets .JA can be turned through an arc of nearly three hundred and sixtydegrees, or from one side of the dischargeconduit around to the opposite side. The side plates 47 are pivotally mounted upon the shaft 4:5,

'- so that their lower ends can be moved out and in from near the center of the working chamber to close proximity to its outer Wall. The frame carrying the buckets 4l is held in working position by means of yohes 53, engaging a band 5st, secured to the side of theworking chamber. These yokes 53 are lreeto slide around on the band and are connected to the side plates 47 by means'of chains and spriligcushions 55. These spring-cushions will perinit .the lower end of the frame carrying the buckets 4d' to yield slightly incase the buck ets should strihe against a rock or other unyielding substance. 0n the' shaft45 is ser cured abeveled pinion 56, i'ntermeshing 4with the corresponding pinion on the short shafts 57, mounted in suitable bearings secured to the turning head 48. This short shaft is con nected to the lower section of thev driving shaft lifby .means of al1-extensible shaft 58,`

consisting of a tubular portion for the reception of a solid portion, as shown in Fig. '16, said parts being keyed together, so that they arefree to move along each other, but are caused to rotate one with the other. The ends of this extensible section are'connected by universal joints `59 to the driving-shaft 14 and the short shaft 57, carried by the turning head 48. This construction permit-s of the raising and lowering of the turning head and 4the -parts carried thereby, and also the lateral shifting of such parts, without interfering The turnwith the operation of the buckets. ing head and the parts carried thereby can be raised or lowered, as required, by any suitable incense-such, 'for example, as that shown, consisting of a rope 60, connected to the stem of the turninghead and passing around guide-pulley 6l and having its oppositeend connected to avsuitable winding-4 drum 62, mounted on the side of the working chamber.

The discharge conduih'which passes up alongside of the tubular shaft or tunnel, is formed of a series of sections of a length. preferably equal to the sections of the tunnel heretofore described, said sections being provided with anges whereby they may be connected together, as clearly shown in Figs. l2, 13, and le.' AThis conduit is preferably made of such a length that its lupper end will be above the level of the Water in which work is being performed. arranged in a frame b, which is preferably independent of the conduit, and is detachably secured on the air-cl1amber or the section of the submerging-tank immediately above the same. The conveyingbuckets 64, which are carried by an endless chain formed of separable sections, are arranged withinthe conduit and head. This chain passes around a driving-pullcy 65, mounted on the shaft 66, passing through the cond nithearhand a pulley 67, mounted ou the shaftv (3S, passing through the lower end of the conduit. The frame l), carrying the conduit-head, is provided with guide-Wings, arranged to move in guides n, 4secured in a recess in the lower end of the submerging-tank, and is. provided at its sides with lugs 70, recessed for the reception of nuts, through which pass threaded rods 7l., saidrods being driven through suitable'gearing bythe band-wheel 72. By the rotation of these rods the conduit-head can be raised or lowered, thereby adjusting the tension of the bucket-chains as required. *Assthe buck- ICO The conduit-head 63 is IZO ets pass around the driving-pulley the contents are discharged through the nozzle 73 of the head into a receiving-basin 74,which forms an enlargement of the pipe 30, heretofore referred to, through which a constant lstreamy of water under pressureis maintained. The dirt, &c., is removed from the basin 74 by this stream of water and discharged into a scow orvother reservoir locatedin convenient proximity to the discharge-nozzle of the basin. A pipe 75 has its lower end connected to the conduit ata point above the working chamber, as shown in Figs. 11 and 15. The upper end of this pipe is held above the level of the water in which the work is being performed by means of a rope 76, connected vto a drum 77 on the shaft 78. This shaft, asshown in Figs. 6 and 7, passes into the working chamber B and is provided with a driving-drum 79, around which is passed a rope 80, extend-A ing down into the working chamber, where it is attached to a winding-drum 81, so that by pulling on the rope 80 the discharge end of the pipe 75 can be raised or lowered, as required. 'i

ln operating my improved caisson, the scow having been secured in position by any suitable means, the caisson is allowed-to move down until its lower end rests upon the bed of the. river or other body of water. Water is then pumped into the sinking or submerging tank E, on top of the airchamber B, through the pipe 82, said tank being formed in sections, as shown; s that a larger' or smaller body of water mayce employed, as required, to sink the caisson?. Airis now forced into the air-chamber and tunnel through the pipe 83, the doors of the air-lock having been closed and sealed. As the pressure accumulates within the caisson any water therein will be forced out through the branch 43, conduit 39, and the pipe 75 until the level of the water in the caisson reaches the level of the opening ofthe branch 43. Workmen can now enter the air-chamber and descend into the shaft, so as to adjust the digging inechanism in the working chamber. If the depth of water in the working chamber is too great, the surplus can be removedby operating the buckets 44, which will raise the water from the lower end of the caisson and discharge it into the pipe 43, the pressure of the air on the water in this pipe and conduit maintaining the water therein ata constant level. By tbc operation of the buckets the dirt is removed from within the caisson and discharged into the branch 4?,down which it will pass to the lower end of the conduit, where it is c'anght by the buckets 64 and raised up and discharged into the basin 7l. The upper end of the conduit is maintained above the level ofthe water in which work is being performed, so that none of the dirt cont ained in the buckets can be washed therefrom and in order that. a pressure in excess of that necessary to balance a coi umn of waterequa? to the depth of water in which work is being done maybe obtained, if desired.

'The pressure of air within'the ailgchamber' 7 and tunnel can be regulated by raisingland lowering the upper end of the pipe 75, which contains the column of water connected with the conduit. By increasing` or decreasing the height of this coluinnof water'contained in the pipe 75 the 'pressurey in .the chamber can be regulatedthat is `to say, by increasing the height of this water column a greater pressure can be maintained. In order to re'- place any water removed by the bucket '64? and insure a column of water within the pipe 75 and in the conduit of sufficient height to balance the air-pressure within the caisson, a supply-pipe 84. Iis arranged so as to discharge water into the conduit, as shown in Fig. '12. When 'in operation, a sufficient quantity of Water in excess of the amount removed by the buckets 64 is discharged into the conduit by the pipe 84, the surpius escaping from the upper end of the pipe 75. In case the man within the working chamber notices a dropping down of the water in the branch 43 he immediately raises the pipe 75 by the rope 7 6, thereby requiring'an increase in the height of the water columns in the conduit and pipe 75v before any further escape of water from the-latter can occur. This increase .in height o f the water columns will connterbalance the increased pressure in the working chamber, which caused a lowering of the water in branch 43.

Vhen it is desired to add sections to the tunnel and conduit', the entire caisson may be raisedr by means of chains 85, connected to the working chamber, as shown in Figs. l and 5, assisted by the block and tackle 86 on the frame surrounding the caisson, until the shoulders 8 on the air-chamber are above the supporting-bracket 7. These brackets are then turned in to support the caisson in its raised position. The .bolts connecting the upper section of the tunnel to the air-chamber and the upper section 39 of the conduit with the adjacent lower section are then removed. The section 3W is then raised by the screws 87, connecting said section with the conduit-head, a sufficient distance to permit of access to the endless chains carrying the buckets (54. A rod 88 is next slipped across the end of the conduit and through the chain, as shown in Fig. 13, to prevent the lower portion of the latter from dropping down and the chains 'disconnected above the rod. The working chamber with the tunnel and conduit are lowered sufficiently to permit of the insertion of new sections in the tunnel and the conduit. New sections are now placed in position and bolted t0 the tunnel and aix-chamber and on the upper end of the conduit. An additional section of conveying-chain is also added and connected to those already in position. The caisson is now raised, so as to permit pf the turning in IIO IIS

eee,

of the supportingbrackets 7 ,and then lowered down to position. ln lieu of raising the V whole caisson, stated, and the disconnect-V the air-chamber, tank, and pipes 30, 82, 83, and 84; by hose orother ostensible pipe convnections. f

As shown in Figr 4, the pumps 895 and 90 for supplying air to the caisson and Water to the tank E may be located on a platform 91, secured to the caisson, and the pipes 30 and 84: connected to the tank, thereby rendering the caisson entirely independent of the float after it has been lowered on the bottom of the river or other body-'of Water. 'When the ioat or scow is moved away from the caisson, the latter should be held from tipping by guys 91, extending to posts or other suitable anchors. y

As shown in Figs. l and 2, the floator scow may be provided with a power-dipper 92, clam-shells 93, and buckets 94 for ordinary dredging operations.

I claim herein as my invention- 1. In a caisson, the combination of an air j chamber provided with an airlock,an openn 35 ended Workingchambenwa tubular shaft or tunnel connecting the airand working chambers, formed of separable sections, and a submerging-tank arrangedron the air-chamber, substantially as set forth.

2. In a caisson, the 'combination ot' an airchamber, a working chamber; tubular shaft or tunnel connecting the air and working chambers,and a Water-sealed discharge-opening from the air-chamber, substantially as set forth.

3. ln a caisson, the combination of an airchamber, a Working chamber, a tubular shaft or tunnel connecting the air and Working chambers, a discharge-box in the air-chamber and extending through the Wall thereof, a pipe or tube for Water under pressure intersecting the discharge end of the boli, substantially as set forth. l

4e Ina caisson, the combination oi' an airchamber, a working chamber, a tubular shaft or tunnel connecting .the air and working chambers, a discharge-box in the air-chamber and extending through the wall thereof, the outer end of said box terminating in a pipe or tube for conducting a stream of water under pressure, and a sealing. lid or cover for said box, substantiallyas set forth.

5. A caisson, having in combination, a Working chamber having an open lower end, and afwater-,sealed U-shaped discharge-conduit having one/arm opening Within the iv ing chamber and the other arm entendi l from the ,working chamber to a point above the level. ci traten",y substantially ser" forth,

6. le., caisson, having in combination, working chamber an open lovverend; a Watersealed conduit extending from the Working chamber to a point' above level:

of the water and vmeans i'or varying the height oi the Water column controlling 'the Water seal, substantially as set forth.

7 A caisson, having in combi working chamber having an open levver a dischargaconduit extending from the n el ing chamber to a point above the level of the Water and provided, within the Working chain ber, with a receiving branch having an open upper end and means ormaintaining the water Within the conduit'at a height not less than the level of Water outsideof the conduit, substantially as set forth. L

8. A' caisson, having in combination, a working chamber having an open lower end,

a discharge-cond uit extending from the Work ing chamber to a point above the level of the Water and provided with a receiving branch, a turning head, Aa conveyer connected to said head, said parts being so arranged that the materialv from the conveyer will be discharged into the brauch in all positions ofthe turning head, substantially as set forth.

9. A caisson, having in combination, an airchamber, a Working chamben'a tubularshaft or tunnel connecting the air and working chambers, a discharge conduit 'extending from the Working chamber to a point above the level of the Water, a conduit-head movably mounted on the air-chamber, an endless chain provided .with brackets arranged "Within the conduit and head, a receiving branch having an open upperlend connected 'to the conduit Withinthe working chamber, and a digging mechanism movably mounted on'the receiving branch, substantially as set forth.

10. A caisson, having `in combination, an air-chamber, a working chamber, a tubular shaft or tunnel connecting the air andworking chambers, formed of separable sections, a discharge-conduit formed of separable sectionsvextending from the Working chamber to a pointabove the level of the Water, and provided with a receiving branch within the Working chamber, a digging mechanism Within the Working chamber, a powerfshaft ex-` tending from lthe air-chamber to the working chamber formed of separable sections mounted in suitable bearings within the sections of the tubular shaft or tunnel, substantially as set forth.

11. A caisson, having in combination, an

IIO

air-chamber, a working chamber, a tubular. shaft or tunnel connecting the air and Worin l ing chambers, a submergingtank. arranged on the air-chamber, a discharge-box arranged Within the air chamber and extending mounted ont-he ioaJt for holding the caisson 1o 'through the Wall thereof, and a pipe or tube in raised position, substantially as set forth.

extending fromthe submerging-tank and in- In testimony whereof I have hereunto set tersecting the discharge endof the box, submy hand. stantially as set'forth.

l2. The combination of a Iioat or scow pro- WILLIAM H' MQFADDEN' vided with guiding posts or supports, a cais- Witnesses: son arranged between said supports, means DARWIN S. WVOLCOTT,

for raising the caisson and supports movably F. E. GAITHER. 

